20.770.080 Tree Density Requirement | Vancouver Municipal Code

20.770.080 Tree Density Requirement.

Click here to view prior versions of this section.

A. Minimum tree density requirement established. The required minimum tree density is 30 tree units per acre for new development; 30 tree units per acre of site disturbance for commercial, industrial and multiple-family (more than four units) development; and 200 tree units for conversion option harvest forest practices. For properties within the City Center and HX districts, the minimum tree density does not apply.

1. The tree density may consist of existing trees, replacement trees or a combination of existing and replacement trees, pursuant to the priority established in Section 20.770.070 VMC. Existing tree units in excess of the minimum density may be required to be retained based on the tree, vegetation, and soil plan review standards of 20.770.070. Required street trees may not be counted toward the minimum tree density requirement except as provided in VMC 20.770.070.B.4.f.

2. When trees are retained in tree tract(s) in a residential subdivision, a higher minimum tree density is set based on the nature of the grove(s); provided, that the creation and establishment of tree tract(s) shall not reduce the housing density allowed on the subject sit under applicable requirements of this Title.

B. Tree density calculation. For the purpose of calculating required minimum tree density, city right-of-way, areas to be dedicated as city right-of-way, and required pervious surface where trees are not appropriate as determined by the City (e.g., athletic fields and water quality facilities), shall be excluded from the area used for calculation of tree density.

1. Tree density calculation for individual trees.

a. Diameter Breast Height (DBH) shall be measured in inches at 4.5 feet above the ground line.

b. The tree unit value that corresponds with DBH shall be found in Table 20.770.080-1.

2. Tree density calculations for heavily forested sites.

a. The average basal area per acre of the dominant and co-dominant stems shall be based upon the inventory of the existing forested stand using forest mensuration techniques.

b. Tree units per acre shall be obtained by multiplying the Average Basal Area by two (2) to obtain the Average Basal Area.

3. Certain areas of a site are required to be improved or set aside for specific purposes. One major objective of the ordinance is to offset the impacts of impervious surfaces with tree canopy. For required pervious areas where trees cannot reside, such as drainage facilities and ball fields, the tree canopy is not critical and therefore, these areas are excluded from the tree density calculation.

4. The required minimum tree density for an applicable parcel is 30 tree units per acre, unless it is a Conversion Option Harvest Forest Practice which will require a minimum of 200 tree units per acre. For proposed additions or site disturbances on existing commercial, industrial, multi-family sites the required minimum tree density is 30 tree units per acre of site disturbance. Specific tree density calculations and replacement tree standards are delineated in the Urban Forestry Manual.

5. Trees required in order to meet minimum tree density shall be planted according to the following priority:

a. On-site;

b. Off-site. When room is unavailable for planting the required trees on-site, then they may be planted at another approved location in the city;

c. City Tree Account. When on-site and off-site locations are unavailable, then the applicants shall pay the estimated cost of the current market value of the trees, including installation and maintenance costs, into the City’s Tree Account established for purchase, installation, and maintenance of such trees.

Table 20.770.080– 1 VMC Tree Density for Existing Trees
DBH	Tree Units	DBH	Tree Units	DBH	Tree Units
1”-6”	1	24”	7	38”	14
6”-12”	1.5	26”	8	40”	15
14”	2	28”	9	42”	16
16”	3	30”	10	44”	17
18”	4	32”	11	46”	18
20”	5	34”	12	48”	19
22”	6	36”	13	50”	20

C. Minimum Size and Tree Density Value for Replacement Trees. The required minimum size of the replacement shall be pursuant to Table 20.770.080-2. Each planted tree shall be equivalent to one (1) tree unit. Larger trees are not eligible to receive credit for more than one tree unit.

Table 20.770.080– 2 Planting Stock Size Requirements
Development Type	Planting Location	Tree Type	Required Min. Size	Tree Unit Value
Residential Subdivision	Tree Tracts	Deciduous	1” Caliper	“1”
Residential Subdivision	Tree Tracts	Conifer	3’tall	“1”
Commercial, Industrial, Multi-Family (4 or more units)	All developed locations	Deciduous	2” caliper	“1”
Commercial, Industrial, Multi-Family (4 or more units)	All developed locations	Conifer	6’tall	“1”
Commercial, Industrial, Multi-Family (4 or more units)	Undeveloped locations (i.e. woodland interplanting, etc.)	Deciduous	1” caliper	“1”
Commercial, Industrial, Multi-Family (4 or more units)	Undeveloped locations (i.e. woodland interplanting, etc.)	Conifer	3’ tall	“1”
Single Family and Multi-family (up to 4 units)	All locations.	Conifer	4’ tall	“1”
Single Family and Multi-family (up to 4 units)	All locations.	Deciduous	1.25” caliper, branched	“1”
Undeveloped Property (Conversion Option Harvest)	All locations.	Conifer/ Deciduous	2-0 Bareroot Seedlings.	“1”

D. Replacement tree quality. Replacement trees shall meet the quality and size standards of this chapter. Replacement trees shall be American Standard for Nursery Stock Grade No. 1 or better.

E. Replacement tree planting standards. Trees shall be planted pursuant to the planting standards delineated herein.

1. For all properties other than those electing conversion option harvest.

a. The species selection and spacing of trees to be planted shall be such that it provides for the eventual mature size of the trees. Soil type, soil conditions and other site constraints shall be considered when selecting species for planting.

b. Replacement trees shall optimize tree diversity; include native species and at least 60% conifers; utilize insect and disease resistant trees unless determined by the Planning Official as not appropriate for the site conditions.

c. Trees shall be watered as necessary to ensure establishment, survival and growth, during the first two growing seasons after planting. Trees shall be mulched with composted mulch 4 inches deep. Staking and fertilizer shall be required where deemed necessary by the Planning Official.

2. Properties Electing Conversion Option Harvest. The following shall apply to Conversion Option Harvest properties:

a. Stocking levels are acceptable if a minimum of 200 tree units per acre of well distributed, vigorous, undamaged trees are established on the site. This requirement includes both existing and newly planted trees.

b. Species chosen for planting shall be suited to the constraints of the site including, but not limited to: soils, available moisture, topography, light conditions, existing and potential disease.

c. Trees shall be planted during the next planting season (October-March) after the harvesting operation is finished. (Ord. M-4341 § 3 (Exh. B), 2021; Ord. M-4179 § 84, 2016; Ord. M-3847 § 11, 2007; Ord. M-3840 § 32, 2007; Ord. M-3701 § 22, 2005; Ord. M-3643, 2004)